1. Field of the Invention
This invention relates to the removal of phenols and other organic compounds from waste waters and is particularly concerned with a method for obtaining the substantially complete removal of these substances by adsorption onto char.
2. Description of the Prior Art
Over a period of the last several years, restrictions on the amount and types of organic materials that may be discharged into the environment have become more severe. In an effort to meet these restrictive standards, there has been a considerable increase in the amount of research and development work devoted to pollution control. One area of considerable activity has been investigations into the use of activated carbon and similar substances as adsorbents for the treatment of waste water containing organic pollutants.
A method commonly employed today for removing organic contaminants from waste water is biological treatment. This technique consists of vigorously aerating the waste water to allow bacteria to carry on their metabolic activity thereby breaking down residual suspended solids and dissolved organic materials by bacterial action. Biological treatment, however, has a serious disadvantage. Industrial waste water normally contains large amounts of nonbiodegradable pollutants which, along with toxic materials present, inhibit or destroy the bacteria thus rendering the biological treatment ineffective.
Studies indicate that the adsorption of organic pollutants by activated carbon is a commercially viable means of treating municipal and industrial waste water which is more effective than biological treatment because the activated carbon will adsorb both biodegradable and nonbiodegradable organic substances in such quantities as to meet present and proposed effluent standards. In addition to using activated carbon for treating municipal sewage and waste water from industrial installations such as refineries and chemical plants, it has also been shown that activated carbon can effectively treat waste water from coking and coal gasification plants. The optimum performance of such an adsorption system has been obtained by proper adjustment of the waste water pH before contact with the activated carbon so that dissolved organic contaminants are in their nonionized and more adsorbable form. The activated carbon will have little or no effect on the waste water pH.
Recent development work, sponsored by the Office of Coal Research, has indicated that certain types of chars, the carbonaceous product resulting from the thermal processing of coal in those cases where the coal is not completely consumed or converted, exhibit adsorption properties similar to commercially available activated carbon and suggests that these chars may be used to treat waste water. This knowledge may be of vital importance in the near future as commercial gasification and liquefaction plants are built. These facilities will produce industrial waste water containing many diverse types of organic substances including cresols, naphthol, phenol and the like. In addition gasification plants utilizing fluid bed gasifiers may generate a large amount of char fines which may contain up to 20 percent of the carbon fed to the gasifier. The use of these char fines as adsorbents to treat the waste effluent from a gasification plant, a liquefaction plant or from other sources will enhance the economics of the gasification process by utilizing the unconverted carbon remaining in the char fines while decreasing the cost of waste water treatment by obviating the need for expensive activated carbon.